1630.7 
Uc-100 
c  .3 


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UNIVERSITY  OF  ILLirjldgj-; A 

Agricultural  Experiment  Station 


URBANA,  OCTOBER,  1905 


CIRCULAR  NO.  lOO 


THE  “GIST’»  OF  FOUR  YEARS’  SOIL  INVESTIGATION  IN 

THE  ILLINOIS  CORN  BELT. 


By  Cyril  G.  Hopkins,  Chief  in  Agronomy,  J.  H.  Pettit,  First  Assist¬ 
ant  IN  Soil  Fertility,  and  J.  E.  Readhimer,  Superintendent  of 
Soil  Experiment  Fields. 


Nitrogen. 

At  ordinary  commercial  prices  the  nitrogen  contained  in  the  air 
above  each  acre  is  worth  more  than  ten  million  dollars.  By  means  of 
bacteria  which  live  on  their  roots,  clover  and  other  legumes  have  power 
to  draw  on  this  unlimited  supply  of  free  nitrogen. 

Potassium. 

The  ordinary,  naturally  well  surface-drained  land  of  the  Corn  Belt 
in  Central  and  Northern  Illinois  contains  in  the  soil  of  one  acre  to  a  depth 
of  seven  inches  sufficient  total  potassium  for  a  hundred  bushels  of  corn 
each  year  for  1900  years,  if  the  stalks  are  returned  to  the  land  directly 
or  in  manure.  The  supply  is  about  36,000  pounds  and  one  hundred 
bushels  of  corn  (grain  only)  contain  19  pounds  of  potassium.  Potassium 
may  be  liberated  from  the  soil  as  needed,  by  means  of  decaying  organic 
matter,  such  as  farm  manure,  clover  residues,  and  legume  catch  crops  as 
green  manures. 


2 


Table  1.  Crop  Yields  ix  Soil  Experiments:  Bloomington  Field: 
,  ;Co^iMfeRciAL  Nitrogen  Series. 

*'  ,•*.  •Tyt'ical  CVitij  Bfdwn  Silt  Loam  Prairie  of  the  Early  Wisconsin 

"  .  Glaciation. 


■  . _ 

*  •  •  • 

•;  .’o 

,  •  • ' 

Plant  Food  Applied. 

1902 

Corn, 

bu. 

1903 

Corn, 

bu. 

1904 

Oats, 

bu. 

1905 

Wheat, 

bu. 

None . 

37 

60 

61 

29 

Nitrogen . 

35 

60 

70 

31 

Phosphorus . 

42 

73 

73 

39 

Potassium . 

38 

56 

63 

33 

Nitrogen,  phosphorus . 

44 

78 

85 

51 

Nitrogen,  potassium . 

40 

59 

66 

30 

Phosphorus,  potassium . 

50 

M  ^ 

/  .■) 

70 

38 

Nitrogen,  phosphorus,  potassium . 

53 

81 

91 

52 

Average  gain  for  nitrogen. .  . . 

1 

4 

11 

6 

Average  gain  for  Phosphorus . 

10 

18 

15 

14 

Average  gain  for  potassium . 

6* 

0 

0 

1 

Average  gain  for  phosphorus  when 

added  to  nitrogen . 

11 

20 

20 

21 

Value  of  this  increase . 

$3.85 

$7.00 

$5.00 

$14.70 

Approximate  Cost  of  25  Pounds  of  Phosphorus. 

In  rock  phosphate . S  .80 

In  steamed  bone  meal .  2.50 

In  acid  phosphate .  3.20 

In  “complete  fertilizer’’ .  8.00 


*Potassium  is  applied  as  a  soluble,  corrosive  salt  which,  like  common  salt,  sometimes 
acts  as  a  stimulant  and  thus  liberates  some  phosphorus  or  nitrogen  from  the  soil. 


Uc 

a  X  ■ 


3 


Table  2.  Crop  Yields  in  Soil  Experiments :  Urbana  PTeld:  Three- 

Year  Rotation:  Legume  Series. 

Typical  Corn  Belt  Soil:  Brown  Silt  Loam  Prairie  of  the  Pearly  Wisconsin 

Glaciation. 


Soil  treatment  applied. 

Corn. 

3  yr.  av., 
bu. 

Oats. 

2  yr.  av., 
bu. 

Clover. 

2  yr.  av., 
tons. 

None . 

77 

48 

1.65 

Legume  (catch  crops) . 

77 

51 

1 .69 

Legume,  lime . 

78 

56 

1.70 

Legume,  lime,  phosphorus* . 

89 

67 

2.47 

Legume,  lime,  phosphorus,  potassium  .  .  . 

91 

68 

2.82 

Gain  for  legume . 

0 

3 

.04 

Gain  for  lime . 

1 

5 

.01 

Gain  for  phosphorus . 

11 

11 

.77 

Gain  for  potassium . 

2 

1 

.35 

Value  of  Increase  and  Cost  of  Treatment. 


Corn. 

Oats. 

Clover. 

Total  for 

3  years. 

Cost  for 

3  years. 

For  legume . 

$  .00 

$  .75 

$  .20 

$  .95 

S  (?) 

For  lime . 

.35 

1  .25 

.05 

1.65 

1.50 

For  phosphorus . 

3.85 

2.75 

3.85 

10.45 

7.50* 

For  potassium . 

.  70 

.25 

1.75 

2.70 

7.50t 

*$7.50  supplies  75  pounds  of  phosphorus  in  steamed  bone  meal.  The  three  crops  have 
removed  only  43  pounds  of  phosphorus. 

tS7.50  supplies  120  pounds  of  potassium.  The  three  crops  have  removed  194  pounds 
of  potassium. 

Note. — On  the  field  where  a  catch  crop  of  clover  was  seeded  in  the  corn  in  1902  oats 
and  clover  were  seeded  in  1903  by  “disking  in,”  without  plowing;  but  the  old  clover  still 
grew  and  smothered  out  the  oats  and  the  young  clover.  Hence  we  give  the  average  of 
only  two  years’  results  from  oats  and  clover  with  three  years’  from  com. 


3  0112  121970112 


4 

Phosphorus. 

If  we  could  draw  at  will  upon  the  total  phosphorus  in  the  first  seven 
inches  of  soil  the  supply  (about  1200  pounds)  would  be  entirely  exhausted 
to  that  depth  during  the  lifetime  of  one  man,  if  hundred-bushel  crops  of 
corn  were  taken  from  the  land.  A  hundred-bushel  crop  of  corn  requires 
seventeen  pounds  of  phosphorus  for  the  grain  and  six  pounds  for  the 
stalks.  Oats,  wheat,  and  clover  also  draw  heavily  upon  phosphorus. 
When  crops  are  fed  the  animals  store  in  their  bones  about  one-fourth  of 
the  phosphorus  contained  in  the  food  consumed. 

By  means  of  decaying  organic  matter  we  can  liberate  each  year  a 
small  percentage  of  the  phosphorus  in  the  soil.  If  we  need  more  than 
we  can  profitably  liberate  from  the  soil,  we  should  apply  it  in  the  cheap¬ 
est  and  most  natural  form,  preferably  as  steamed  bone  meal  or  as  finely 
ground  raw  rock  phosphate  in  connection  with  manure  or  clover.  Steamed 
bone  meal  is  really  a  farm  product  and  raw  rock  phosphate  is  a  natural 
plant  food  material,  and  neither  will  ever  injure  the  soil.  The  use  of 
acidulated  manufactured  fertilizers  is  not  advised. 

Results. 

On  the  Bloomington  experiment  field  for  the  three  years,  1903,  1904, 
and  1905,  we  applied,  in  all,  300  pounds  per  acre  of  commercial  nitrogen 
at  16  cents  a  pound,  75  pounds  of  phosphorus  at  10  cents  a  pound,  and 
120  pounds  of  potassium  at  6^  cents  a  pound.  We  removed  from  the  best 
yielding  plot,  in  the  three  crops,  corn,  oats,  and  wheat,  287  pounds  of 
nitrogen,  45  pounds  of  phosphorus  and  176  pounds  of  potassium,  per  acre. 
Measured  by  the  crop  yields,  we  have  gained  (on  the  best  yielding  plot) 
13  pounds  of  nitrogen  and  lost  (as  an  average  of  four  plots)  $39.65  of 
the  $48  invested  in  dried  blood;  we  have  gained  30  pounds  of  phosphorus 
and  have  also  gained  $12.35  in  money  above  the  $7.50  invested  in  steamed 
bone  meal;  and  we  have  lost  56  pounds  of  potassium  more  than  we  applied 
and  we  have  also  lost  $6.80  of  the  $7.50  invested  in  potassium. 

For  more  detailed  information  regarding  methods  of  soil  improve¬ 
ment,  cost  and  methods  of  applying  plant  food  materials,  comparative 
value  of  steamed  bone  meal  and  raw  rock  phosphate,  systems  of  crop 
rotations,  the  use  of  legume  catch  crops,  etc.,  see  Circulars  87,  96,  and  97, 
which  will  be  sent  free  of  charge  upon  request. 

Any  one  interested  in  Illinois  Agriculture  can  have  his  name  placed 
upon  the  permanent  free  mailing  list  for  all  circulars  and  bulletins,  upon 
his  own  request,  which  should  be  made  by  letter  or  postal  card  addressed 

Agricultural  Experiment  Station, 

Urbana,  Ill. 


